The long term objective of the proposal is to study the role of the extracellular matrix (ECM) in morphogenesis. The organ of choice is the embryonic skin and the ECM components are the proteoglycans. Previous results have indicated that embryonic skin contains several discrete populations of proteoglycans that may differ both in their core protein and in their glycosaminoglycan side chains. Of the three proteoglycan populations identified, one can interact with hyaluronic acid and one is intercalated in the cell membrane. In an effort to understand the function of these two proteoglycans, their structure will be determined by deducing the entire amino acid sequence of their core proteins from cDNA clones that will be generated (Aim #1). The functional properties of these proteoglycans will be determined by identifying other matrix proteins and cells with which they may interact. The specific domains on the proteoglycans that are involved in the interactions with other matrix molecules and cells will be identified and characterized using the recombinant DNA and immunological tools developed (Aim #2). The temporal and spatial appearance of the proteoglycan transcripts will be determined with the cDNA probes in situ hybridization experiments and this information will be correlated with the appearance of the translation products and with the localization of other ECM macromolecules (Aim #3). Based on the observation that the intercalated heparan sulfate proteoglycan is no longer synthesized in cell culture, an investigation will be undertaken to determine the role of the integrity of the skin tissue in the transcriptional and translational regulation of the synthesis of the proteoglycan (Aim #4). The possible relationship between the intercalated proteoglycan and the cytoskeleton will also be investigated (Aim #5). Finally, genomic clones coding for the two skin proteoglycan core proteins will be isolated in an effort to study the organization of the gene and to obtain putative regulatory sequences for these genes (Aim #6). These studies will be carried out on the dorsal (feather forming) and tarsometatarsal (scale forming) regions of normal embryos and on comparable regions of scaleless embryos, which, as a result of a hereditary lesion, fail to develop feathers and skins.